UrvKd S'.aies            Ofnce o! ^es'.coes
                 Envron~-.er.ta! °roiection      and Toxic Su'jstiT-.ce^
                 Agency               (H7501G           540/FS-92-170
EPA          Pesticide
                 Fact Sheet
                 Name of Chemical:   CLETHODIM
                 Reason for Issuance:   NEW CHEMICAL
                 Date ISSUed:  January 28, 1992

                 Fact Sheet Number:  230
       Description of Chemical
      Chemical Name:  (E)-(+)-2-[l-[[(3-Chloro-2-
      Common and Other Names:   Clethodim
      Trade Name:    Select
      EPA Shaughnessy Codes:    121011
      Chemical Abstracts Service (CAS)  No.:    99129-21-2
      Year of Initial Registration:  -1991
      Pesticide Type:     Herbicide
      Chemical Family:     Cyclohexanedione
      U.S. and Foreign Producers:  Valent U.S.A.  Corporation

      Use Patterns and Formulations

      Application Sites-: Postemergent treatment on soybeans and  cotton
      for control of grasses
      Types and Methods of Application:   Foliar application by  ground
      Application Rates: 0.094 -  0.25 Ib  ai/acre
      Types of Formulations:   25% emulsifiable concentrate  (EC)
      Usual Carriers: Mix  with water

      Science Findings
      Summary Science Statement

           Review  of   the  product   chemistry,   environmental   fate,
      toxicology,  ecological effects and residue chemistry data have been
      completed.  The available data support conditional registration of
      Select for  control of annual and perennial grasses in  soybeans and
      cotton.   Results   of  acute  toxicity studies   indicate  Toxicity
      Category III ^(Caution).   Chronic studies present  no evidence of
      unacceptable 'health  hazards  resulting   from  the  proposed uses
      Ecological  effects data  indicate  that the proposed use on  cotton
      and soybeans will result in minimal risk  to avian,  aquatic and
      mammalian species.

     Clethodim and  degradates  do not  show persistence  in field
dissipation studies. No significant bioaccumulation occurs in fish.
Since  it  is easily  degraded  both by photolysis  and  aerobic
microbial  action,  clethodim  does  not  seem  likely to  threaten
surface  water.     Under  present  use  patterns  and  under  most
circumstances,  clethodim  does not appear  likely  to  threaten

Chemical Characteristics:

Physical State:

Molecular Weight:

Molecular Formula:

Viscous liquid

Clear amber
Melting Point

Boiling Point



Vapor pressure:


partition coefficient:



Storage Stability




1.395 g/cu.cm 20 C

Limit, g/100 mL solvent at 25 C

1 x 10~7 torr

pK2 =4.47

Kow = 1.5 x 104

4.1 in a stirred solution
or 4.2 in a standing
solution 4.9 (5% aqueous

Flashpoint 110 *C


< 1% and  <  3%  degradation in glass
containers and aluminum containers,
respectively, after one year of
storage at 21 *C

          100 cps at 20 'C



Dielectric Breakdown



Toxicology Characteristics:
Acute toxicology results:
(Technical  (T) 83.3%  &  96.ai:)

Acute oral toxicity-(rats):  98.6%
Acute oral toxicology-(rat):  83.3%

Acute oral LDso(mice) :  83.3%

Acute Dermal LD50(rabbit)  83.3%

Acute inhalation LD50  (rat):  83.3%

Primary eye irritation(rabbit)  83.3%

Primary dermal irritation(rabbit)

Acute Toxicity (Select Herbicide)

Acute oral toxicology-(rat):  26.1%

Acute oral LD50(rat):  26.1%


Acute Dermal LD50(rabbit) 26.0%
LD50(female)  greater  than
1.4 gm/kg category  III

LD50(F)=1.36  gm/kg
toxicity category III
LD50(M)  1.63%g/kg

LD50(M)=2.57  g/kg
    LD50(F) =2 . 43g/kg
toxicity category TTI

LD50(KaFji greater than
5 g/kg toxicity  category
LC50 greater  than
toxicity category III

toxicity category IV

26.1 and 26.0% ai)

 LD50(F) 2.92g/kg
 LD50(M) 3.61%g/kg
 tox.  category III

LD50(M)=3.61  g/kg
toxicity III

LD50(M&F) greater than
5 g/kg tox.category

Acute inhalation LC50(rat) : 26.1%*
Primary eye irritation

Primary Dermal irritation
(rabbit): 26.0%

Dermal sensitization:

Subchronic Testing
LC50 greater than
5.4 mg/L(M&F)(0.33 mg/L)
toxicity category II

tox.category III

     21-Day Dermal (rat)- The systemic NOEL is 50 mg/kg/day.  The
LOEL for skin is 10 mg/kg/day (26.3%).

Chronic Testing


     In  the 18-month  carcinogenicity  study,  mice  administered
clethcdin  (83.3%)  at dosages of  0,  20,  200,  1000,  or  3000 ppm
resulted in a systemfc  NOEL and  LOEL of  200 and 1000 ppm  (HOT) for
male and female mice, respectively.

     Chronic toxicity

     In a  1-year feeding study, dogs  were treated with clethodim
(83.3%) at dose levels of 0, 1,  75, or 300 mg/kg/day.  The
systemic LOEL for  both sexes is 75 mg/kg/day based  on increased
absolute and relative liver weights and alterations in hematology
and clinical chemistry.  The NOEL is 1 mg/kg/day.

     Chronic toxicity/Carcinogenicitv - (Rats)

     A 2-year chronic toxicity/carcinogenicity study with rats fed
clethodim  (83%)  at dosages of 0, 5, 20,  500,  and 2500 ppm.
Liver weights were  not affected at study  termination nor were there
any compound-related histological changes noted (HOT).   The
systemic NOEL  is  500  ppm  (19 mg/kg/day), based upon the liver
weights were not effected at the study termination nor were there
any compound-related histological changes noted.  The systemic LOEL
is 2500 ppm (100 mg/kg/day).

     A rat teratology study was  conducted with clethodim (82.6%)
using doses of 0, 10, 100,  350,  and 700  mg/kg/day.  Based upon
reductions in body weight gain and clinical signs of toxicity,


the NOEL and  LOEL for maternal toxicity are 100 and 350 mg/kg/day
respectively.    Based on  reductions  in  fetal  body  weight and
increases in skeletal anomalies the NOEL and LOEL for developmental
toxicity are  100 and 350 mg/kg/day,  respectively.

     A rabbit teratology study was conducted using doses of 0, 25,
100, and 300  mg/kg/day  (clethodim 82.6%).  Maternal toxicity was
manifested by clinical signs of toxicity, reduced weight gain and
food consumption during  treatment.   The NOEL and LOEL are 25 and
100  mg/kg/day,  respectively.    Developmental  toxicity was not
observed.  The NOEL for this endpoint is 300 mg/kg/day.

     A rat teratology study was conducted using doses of 0,  10,
.100, and 700  mg/kg/day  (clethodim 98.6%).   The maternal NOEL and
LOEL  are  10  and  100  mg/kg/day,  respectively.    Based  upon
significant  reductions  in fetal  body  weight  and  litter  size
significantly increased litter and fetal incidence of cervical rib
at 700 mg/kg/day, the NOEL and LOEL for developmental toxicity are
100 and 700 mg/kg/day, respectively.


     In a reproductive toxicity study, rats were fed doses of  0, 5,
20, 500, or 2500 ppm.  The NOEL and LOEL for systemic
toxicity are 500 ppm  (51 mg/kg/day) and 2buu ppa  I>DJ ag/kg/aay) >
respectively, based on reductions in body weight, particularly in
males, and  decreased food consumption  in both generations.   No
effects  on  fertility,   length  of  gestation,  or   growth  and
development of offspring were  observed.  The NOEL for reproductive
toxicity is 2500 ppm  (HOT) (83.3%).


     Technical material was not mutagenic in the Ames assay.

     Metabolism - Rats

     The  requirement for  a  metabolism  study  in  rats has  been
satisfied.  Five groups of rats,  5 males and 5 females, were
dosed in  various sequences with either 4.5  or 450 mg/kg   [14C]
clethodim orally.

     Clethodim is readily absorbed and eliminated with essentially
all of the [   C] dose recovered from urine.  Several days after the
compound was« administered, smaller  amounts  were  recovered  from
feces (9-17%)  and  expired air.    Gastrointestinal  absorption was
estimated at  89-96%.   There  was no  evidence  of bioconcentration
following multiple exposures; the  adrenal dosing  had the highest
concentration of radiolabel (0.07 to  0.22 ppm for low and repeated
doses; 5.4 to  13 ppm for high-dose rats). Clethodim was extensively
metabolized with < 1 percent  eliminated


as  the unchanged  parent  compound.   The  predominant  metabolite
recovered was clethodim sulfoxide (48  to  63% of administered label
after 48 hours).

     Environmental Characteristics

     Hydrolysis: Propyl [  C]-clethodim degraded with half-lives of
26 days (pH 5) and approximately 300 days  (pH 7 and 9).
Allyl-labeled clethodim degraded with half-lives of 42  days(pH 5)
and 360 days  (pH 7).  The degrades were clethodim.oxazole. and

     Aerobic  Soil  Metabolism-  Under aerobic  soil  conditions,
clethodim degrades with a half-life of 1 to 2.6 days.

     Anaerobic  Acruatic Metabolism -  Results of the  anaerobic
aquatic metabolism study indicate that clethodim has a half-life of
128 days in the aqueous phase  and  214 days in the sediment.   The
degradates formed are metabolized  as  rapidly  as  they  are formed,
and do not appear to accumulate.
     Aqueous Photolysis -   Clethodim  degrades with half-lives of
1.5-9.3 days, at pH 5 and 9, respectively.

     Mobility - Leaching and absorption/desorption.  Clethodim and
its sulfoxide, sulfone, and oxazole sulfone degradates are weakly
absorbed into two sandy loam soils,  clay loam,  sandy clay loam, and
sandy soil.                    . .

     Soil Photolysis - Photolysis of clethodim on soil will not be
a major pathway of degradation, since metabolism is rapid.  After
7 days, less than 6.8% of parent compound remained.  Little or no
volatile material, organic or C02 was produced.   The single major
product  was  clethodim  sulfoxide.    Metabolism   is  the  primary
mechanism of degradation.

     Terrestrial Field Dissipation -  No  vertical  movement of the
residues was observed as all measurable residues were confined to
the top 20 cm of the soil.

     Accumulation - In Confined Rotational Crop and in  Fish - In
rotational crops, some uptake and concentration were detected at an
exaggerated rate of 4 X  the maximum single application.   Closely -
related  metabolites  accounted  for  around  1/3  of  the  total
radioactivity  observed   in    the    plants.    No   significant
bioaccumulation occurred in fish.

     Ecological Characteristics:
      Available fish and wildlife data indicate that the proposed
uses  on cotton and  soybeans  will  result in  minimal  hazard  to
nontarget and endangered beneficial insect, avian, freshwater


fish and mammalian species.

     Clethodim is slightly to practically non-toxic to birds .  The
avian acute oral LD50 was greater than 2000 mg/kg for the bobwhite
quail and the avian dietary LC50is were > 4270 ppm for the bobwhite
quail and > 3978 ppm  for  the mallard duck.  The mallard and avian
reproduction  study  is acceptable  and  fulfills  the  waterfowl
guideline requirement. An NOEL of 1000 ppm was reported.

     Clethodim technical is slightly toxic to cold-and warm-water
fish species. The fish LC50 for  the rainbow trout is 18.0 ppm and
33.0. ppm for the blueqill sunfish. Select EC is slightly toxic to
Daphnia macrna. The 48 hour UC$Q value for Daphnia magna is 20.2
mg/L; and the NOEL is  5.5  mg/L.  The  formulated product was tested
because  of  a high  level   of  a  certain  inert  ingredient  in  the

     Clethodim technical and Select 2 EC are practically non-toxic
to honeybees,with an LD50 of greater than 100 ug/bee.  Select 2 EC
was evaluated to assess the toxicity of formulation inerts.

     Tier  I and  II  non-target plant phytotoxicity data  using
technical  Clethodim were  submitted. The  data demonstrate  that
Select 2 EC  is  extremely  selective in its mode of  action.   Only
grass species are  at  risk from off-target movement.   Endangered
grass in or arenni Select-1-re?_*•?? *'<. ^H«JV f^om around or
aerial applications.  Thus,  Select  is prohibited  from use in the
counties listed under "Summary ox Regulatory Positions."

Tolerance Assessment  - A  tolerance with  an  expiration  date  is
established for residue of the herbicide Clethodim (ANSI) , (Ł)-(+)-
(ethylthio)propyl]-3-hydroxy-2-cyclohexen-l-one,    and    its
metabolites containing the 2-
cyclohexen-1-one moiety in/on soybeans  at 10 ppm; cottonseed at 1
ppm; meat,  fat,  and meat byproducts of cattle, goats, hogs, horses,
poultry,  and sheep at 0.2  ppm; milk at  0.05 ppm; eggs at 0.2 ppm;
soybean soapstock at 15 ppm; and cottonseed meal at 2 ppm.

Summary of Regulatory Positions

Use,   formulation,   manufacturing  process   or   geographical
restriction:  " Do not apply directly to  water," "Do not apply
where runoff  is likely to occur.11  "Do not  apply where  weather
conditions favor drift from areas treated.  Do not allow Select to
come in  contact with  desirable grass crops  such as  corn,  rice,
sorghum,  small grains, or  turf as these other grass crops will be
injured or killed." "Minor leaf spotting may occur on soybeans and
cotton under certain environmental conditions.   New foliage is not
affected."  Do  not  apply  a broadleaf (herbicide) within  one  day
following application. Do  not apply by air."

        Select 2EC is prohibited from use in the following counties to
   avoid non-target injury to the endangered grass species listed: (1)
   Solano grass-Colusa,  Contra, Costa, Fresno,  Glenn, Madera, Merced,
   San Joaquin,  Solano,  Stanislaus and Tehama Counties in California,
   and (2) Texas wild rice - Hays county in Texas."

        Summary of Maior Data Gaps

        Revise analytical method  and have  a  successful independent
   laboratory validation conducted on the revised method.

        Contact Person at EPA

        Joanne I. Miller
        Product Manager (23)
        Fungicide-Herbicide Branch
        Registration Division (H7505C)
        Office of Pesticide Programs
        Environmental Protection Agency
        401 M Street SW.
        Washington, DC  20460

        Office location and telephone number:
        Pan. 245,  Crystal Mall #2
        1921 Jefferson Davis Highway
        Arlington, VA  22202
        (703) 305-783.0     .                    .                   , :. .

        Disclaimer:  The information in this Pesticide Fact Sheet is
   a summary only and is not to be used to satisfy data requirements
   for  pesticide  registration  and  reregistration.   The  complete
   Registration Standard for the pesticide  may be obtained from the
   contact person listed above.
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